what you gon' do (when there's blood in the water)
by Terapsina
Summary: The obligatory 'Mary finds out Kate is Batwoman in the most stressful manner possible' fic.


**Disclaimer**: Not mine.

**AN**: I actually wrote this and two other fics for this fandom quite a while back but at the time there wasn't a category for them yet so I only posed it on AO3. But I noticed it's here now so I thought I might as well post it now. This was written before 1x03.

*o0O0o*  
***what you gon' do*****  
*****(when there's blood in the water)***  
*o0O0o*

Most times Mary doesn't mind having long days, she would never have made it through almost two and a half years of medical school, let alone added running an illegal clinic to her resume, if she couldn't cut it on four hours of sleep and power naps all over the place - well, if she could add that to her resume without promptly landing across the desk from her head of the Crows step-father as he just sat there… and stared, silent and furious, or worse… called her mother.

But most days aren't today. And today she's been up since 4 am because of an attempted bombing at a housing complex in the poorer part of Gotham. The bomb itself hadn't hurt anyone - Mary heard that apparently Batwoman had jumped on it, taking the brunt of the explosion with her body armor - but the evacuation had caused a panic and there'd been a stampede.

Which meant that those hurt that had the means probably went to Gotham Central Hospital. And those without health insurance who couldn't afford to pay two thousand dollars or more for a broken arm, went to her. So yeah, it's 2 am of the next night and she's running on four cups of coffee and one ten minute nap six hours ago.

She considers if she needs another cup to get through getting home but decides that would probably bite her once she's in her nice warm bed, lying on her Egyptian cotton sheets and can't close her eyes.

Mary's actually almost out of there when there's three neat knocks on the metal doors of her clinic. Mary stops in place, - her bag almost over her shoulder - and groans aloud. Or sobs, it might have been a sob.

She drops the bag and walks for the door, reaching it, she lightly hits her head against the cool metal before gathering enough strength of will to actually open the door.

If no one's dying she might kill them herself.

-or - and she might just be spit-balling here, a hysterical corner of her mind chimes in - she might be the one who's about to die.

The person on the other side of the door is Red Alice and tonight she's really seemed to have earned her name, because she is _covered_ in blood.

Mary opens her mouth for what promises to be the loudest, most high pitched, blood curdling scream in her arsenal when Alice _moves_ and slams her palm over Mary's mouth, the other one lands on her throat, squeezing - just slightly but Mary gets the message.

"Quiet like a mouse, my dear. Cats are on the prowl and we don't want them on our tails." Alice snaps at her, eyes flashing.

Gasping and trying to think past the terror, she tries to remember where she'd put the gun Beatrice - the mother with no insurance and a son with a severe peanut allergy - had given her after the _last _time Alice had directed her attention toward Mary. But it's locked inside the drawer of her desk, and her desk is in the other room. There's no way she's getting to it before Alice does whatever she came here to do.

"What… what do you want?" Mary rasps out as soon as Alice's left hand leaves her mouth - her right is still dangerously close to a carotid artery. She doesn't want to think about exactly how fast Alice can go for one of those knives she likes to play with so much any time she drops a video message for Gotham.

"You're going to put all the red, red rubies back inside her chest or I'm going to bleed them out of you instead." Alice singsongs, eyes pointedly sliding sideways.

Mary's eyes follow her and land on a second person she hadn't noticed in her initial terror over seeing Gotham's most wanted. Though the fact that the woman who's slumped against the wall a few feet away is wearing all black might have helped conceal her in those first moments, now though Mary can't look away from the shock of red hair lying in a mess around her masked head. The identity of the body is unmistakable.

Batwoman is unconscious and bleeding out in front of her clinic, with something that looks like the length of an arrow sticking out of her stomach. So Mary's got a homicidal villain and a potentially dying vigilante on her hands and… wow, she really regrets not drinking that fifth cup of coffee.

Mary's mind is blank with confusion, - exhaustion - the scene just doesn't make sense. Since the Batwoman's appearance months ago there's been dozens of reported clashes between her and Red Alice in the news.

"Why would you want me to save Batwoman?" She asks, her heart - which had already been running - feels like it's just picked up even more speed and is well on the way to beating its way out of her chest.

She tips a bit forward to get a better look, still careful of Alice's uncertain motives, and the door she'd opened moments before slides open a little wider. She knows that Alice says something then but she doesn't hear it past the buzzing in her ears, the light from the doorway has moved and landed on the lower half of Batwoman's face.

"Oh, God." Mary gasps and pushes Alice away, no longer caring about the threat she brings to her. "Kate!"

In a moment she's on her knees beside her sister, assessing the injury. Penetrating trauma to the upper right abdomen. She's breathing but Mary can't get at her pulse, the armor that somehow hasn't protected her from whatever happened is instead getting in the way of Mary's attempt to get at a pulse point. She doesn't like how cold her face is to the touch though.

"Kate!" Mary tries to rouse her, slapping her lightly at the cheek. "Kate, can you hear me? Can you open your eyes?"

There's no response. All her years at med-school have taught her how bad that is. Kate needs a hospital, she needs… she- Mary takes in the picture Kate makes and falters. She can't take Batwoman to a hospital, which means she can't take _Kate_ to a hospital. Because if Kate is Gotham City's new vigilante then the moment she gets identified she'll get arrested, and getting arrested will get her killed.

For a moment Mary doesn't know what to do and then her eyes land back on the murderer on her clinic's doorstep.

Alice is standing frozen, looking at Kate with a dazed expression, like reality isn't really sinking in yet.

Two months ago this woman sent someone to kill her. And Mary would like nothing more than to get as far away from her as possible but right now she's the only person around who can help Mary save Kate. Which is clearly a sentiment Alice shares or she would never have brought her here in the first place.

Smothering all other instincts Mary does what she has to.

"Help me get her inside." She orders.

Alice doesn't react, still staring at Kate.

"Alice." Mary tries again."We need to get her inside, Alice! Alice! _Beth!_"

That seems to have finally done it, because she lurches down to her knees to grab Kate by one of her arms while Mary goes for the other. Together they hoist Kate to her feet and start dragging her inside the building.

"How do you take this off?" Mary asks a minute later as soon as she has hastily disinfected the surface of the table she's planning to put Kate on. First though they need to get her out of that armor.

As soon as Alice starts undoing something behind Kate's back Mary joins her. They manage to free her from the costume without jostling the arrow too much and then finally Mary can see what she's dealing with.

Kate's pulse is steady but weak, which indicates she's gone into Hypovolemia but she's not quite in danger of her heart stopping. Yet. She needs a blood transfusion.

First things first she grabs two pairs of surgical gloves and throws one toward Alice. "Put those on!"

"Bossy." Alice says and _tut-tuts_ at her. Normally that would call for a more involved response but she follows her instructions so Mary just throws a hurried glare at her and lets it go.

As soon as their hands are covered by the latex gloves she pours some more of the disinfectant over them and then guides Alice to place her hands over Kate's abdomen, carefully encircling the arrow in a way that makes sure it doesn't move.

"Put pressure there." Mary says and turns to run toward the back of the room to get her blood transfusion kit, she falters as she remembers Kate's blood type. She doesn't have any B negative blood and she's fresh out of the O neg. She spins back around. "What's your blood type?"

"What?"

"Your blood, do you have the same type as Kate?" She snaps, irritated at the delay of this conversation. At any other time she'd be far too terrified to yell at a known killer, right now she's far more terrified of watching her si- watching Kate bleed to death.

"Yes. I think so." Alice says.

"You think so, or you're sure?" She asks, voice harsh, she's moving again taking the kit and starting to unpack it so that if she gets the answer she needs she's ready to do her job at once.

"I'm sure." Alice says and her voice hardens with certainty. "We got tested in school. B negative?"

Mary exhales in relief and moves to insert the needle in Kate's arm. Then she does the same to Alice and tries not to think too much about it.

Saving Kate's life first. Figuring out how to survive the night in case Alice still plans to finish the job she started by sending her ax-happy boyfriend after her? Later.

—

The next half an hour had turned into a hectic rush of removing the arrow from Kate's abdomen - which luckily hadn't penetrated as deeply as Mary had feared - and replacing her lost blood with Alice's before it became too dangerous for the donation to go on, and Mary was forced to replace the blood with a saline solution.

Getting the arrow out might have turned into more of a struggle than it would have been if the arrowhead had gone out her back but at least it had avoided piercing any of the major organs. It hadn't actually even nicked her large intestine which is good because Mary doesn't think she could have fixed that.

She's already done more tonight than she's entirely comfortable with doing inside the sub-par facilities available, actually. Or, you know, with still having a year and a half of medical school left to go.

And Red Alice is still only a few steps away from her.

Though at least now that she's donated so much of her blood to Kate she should be woozy enough that Mary might be able to knock her out if the situation calls for it.

And Kate is stable.

Which means Mary's mind is pulling back from the emergency mode of_ 'Kate is dying' _and switching gears to _'Kate is Batwoman'_.

Which she hadn't told Mary. Despite the fact that they've spoken more in the past two months than they had in the past five years combined, or the fact that Mary had thought they might actually have been starting to build the relationship she'd given up on ever sharing with her, or the fact that Kate knew Mary's big 'go-to-jail-if-ever-found-out' secret but at no point even hinted at her own.

A secret that _Alice_ obviously knew. Because of course she did, because somehow a mentally unstable villain was more trustworthy than Mary.

The feeling blooming inside Mary's chest is ugly and unfair, there's a dozen other reasons for why Alice might have found out Kate's secret, it's also a feeling Mary's very familiar with.

She's been envious of Beth for almost twelve years. Not because she wanted to steal the affection Kate had always held like a torch in wait for Beth to come back, - or because she wanted to replace Beth - but because she's always wanted to share in that affection.

Because she's never heard Kate call Mary her sister. Not even her _step-_sister. Even when Kate had cause to introduce someone to her it would never be:_ 'This is Mary, my stepsister.'_ it was always ever and only _'This is Mary, our parents are married.'_

It had never failed to make something sharp twist inside her chest.

Enough. She needs a distraction from this pointless carousel of feeling not quite good enough, so she turns away from Kate and moves toward the discarded pieces of the suit that was left at the side of the room once they'd gotten it off Kate.

Something about the front of it catches Mary's eye. The black armor isn't pristine with one hole on the suit's frontal side like she'd guess would be the case if it got hit with some kind of armor-piercing arrow - are those a thing? Because she's heard rumors about Star City.

The suit looks damaged, bent inward and cracked in something almost like a spiderweb pattern. There's jagged almost melted looking spots on it, especially around the lower torso. It looks as if… - her mind jumps back to what she'd heard from a few of today's patients, about Batwoman jumping on top of the bomb.

"What exactly happened?" She asks before she can think better of attracting Alice's attention.

"What always happens." Alice says from close behind her. Mary forces herself not to jump out of her skin. "A lucky shot by a pathetic mouse on a bad, sad, mad day and the bat fell down. Oh well, you live, you learn, you chop a few heads tomorrow."

Alice is a bit unsteady on her feet but not as much so as Mary might have hoped, and that intense focused stare is back on her face. The focus entirely on Mary.

Mary knows not to flinch. Besides, there's something almost familiar about Alice's eyes, they're angry and wounded and lonely. She sees Kate in them, which she guesses means she's seeing Beth in them.

She's just not sure if that's very good or very bad.

"What are you going to do?" Mary asks. Or starts asking because there's the sound of a broken glass pane hitting the floor and shattering from a room above them. The building is abandoned. That's why it's perfect for Mary's purposes. Somehow Mary thinks it's too much to hope that some homeless animal has found itself wandering onto the property.

"Oh. I love a mouse trap." Alice says as she throws back her head with a smile. Then she grabs Mary's shoulders and pulls her closer. "Go make sure Katy-Kate is all tucked in and hiding behind the Bat, okay? I'll be right back."

And then she's gone.

The first thing Mary does is pocket the thing she's been trying to get her hands on without being observed for the past half an hour. The second thing she does is go for the costume. There's no way Mary has enough time to dress Kate back into Batwoman but she doesn't need to put on her the whole thing, just the mask. And that she does quickly enough.

Kate looks _ridiculous _and Mary mourns the fact that she doesn't have time to take a picture - not that she could anyway, with all these hackers rising up from shadows recently, both the villainous type and the plain gross ones.

She's finished by the time the ominous silence that's been covering the clinic since Alice left, gets broken by something heavy and soft hitting something wooden.

She leaves the room and then knocks a closet filled with clean linens over the doorway, quickly she makes sure it's jammed in place so that if anyone tries to move it to get inside at Kate, Mary will be able to hear it. Then she runs toward the sounds of laughter and smashing glass and breaking furniture from one of the inner rooms. Which tells Mary she probably knows where Alice and their uninvited guest is.

The room the fight is taking place in is the one where Mary had moved all of the too damaged furniture coming with the building. It wasn't a neat place to begin with and now it looks like a hurricane has gone over it.

Alice is grinning, teeth bared and trying to remain standing by one of the walls. She's also pale and breathing too hard, the blood she'd donated clearly finally catching up with her. There's one of Mary's scalpels in her hands and a smashed lamp by her feet.

The man is with his back to Mary on his knees, arm bleeding. And he's reaching for the hunting crossbow by his feet.

Mary doesn't so much think as react as she grabs the closest heavy object at hand - another old lamp that wouldn't turn on - and smashes it over the guy's head.

He drops like a particularly heavy stone.

"Are you okay?" Mary asks on reflex and lets the lamp fall out of her hands to the floor.

"You know, I think I might be starting to like you." Alice says at her, though her smile hasn't lost its savage look, there is however a hint of actual interest in her eyes. Mary shudders, she's not sure if that's actually better. Then Alice's eyes go back to the unconscious man Mary's guessing shot Kate, and all hint of humanity drops from her face like she's a snake shedding the skin that doesn't quite fit. She takes a step for the man, the scalpel in her hand twisting around with a play of fingers and Mary panics.

"No, stop!" Mary says and rushes to stand in front of Alice. "You don't have to kill him. He didn't see Kate. I'll have some guys drop him off somewhere in the morning and make an anonymous tip. He'll be arrested, he's not a threat anymore."

"Really now? And how will you do that, he's gonna wake up any minute now. And we can't have that, now can we?" Alice says, eyes still intent on her target.

Mary's face hardens, her hand going into her pocket. Then she turns around - turns her back to Alice, a panicked voice in her head adds - and drops to her knees to inject the liquid from the syringe she'd been hiding, into the man's bloodstream.

"He'll wake up when I want him to wake up. And no one's murdering anyone inside my clinic. It's off limits." She says and gets back to her feet.

Alice just stares at her, her lips pressed in irritation, the look on her face that of a child that's being told there's no sweets for dinner.

"Fine." She snaps. "I'm not going to kill him here."

"Good." Mary says, dropping from her protective stance. Relieved that she doesn't have to risk her life to protect a man that almost killed Kate. Her eyes move down to the scalpel Alice is still playing with. "Can I have that back now, please?"

"No." Alice says and tilts her head sideways, looking at her with thoughtful eyes. "Mine now."

She opens her mouth to argue but then closes it, all things considered a scalpel is probably the easiest of the stuff she'd used up tonight to replace and she doesn't want to risk setting Alice off.

"Be a dear, tell my sister I won't always be there to pull her wings out of the fire. And don't sing to Daddy's crows, I wouldn't want to have to come back." She says and makes the scalpel vanish into one of the pockets of her blue coat, before twisting dramatically on her heel and starting to walk out of the room and away from both Mary and the room Kate's still in.

"I wouldn't do that." Mary yells toward Alice's turned back and almost adds how Kate's her sister too. What holds her back is not so much the potentially suicidal results of those words as the fact that Kate would probably disagree.

She wouldn't say it, Mary knows that much at least, but she'd think it and that's painful enough.

After Alice is gone Mary turns around toward the knocked out and drugged man and sighs. "Now, how the hell am I gonna move you?"

—

It takes another hour before Kate starts stirring.

In that time Mary has managed to drag the man into the room and wrapped up his bleeding shoulder - though she's left him on the floor by one of the walls, which as far as she's concerned serves him right… even if it had more to do with there being absolutely no way for her to lift him up onto one of the old spring-mattress beds than anything else.

She'd also taken off Kate's mask again now that the threat of her being identified as Batwoman was over, _and_ made herself that cup of coffee she'd decided against before she'd been so rudely interrupted from going home.

She hears Kate groan and walks over.

"Drink this." Mary says and passes Kate a glass of water as soon as she opens her eyes and starts trying to get up. Then she puts an additional pillow under Kate's head to help her stay upright. "You're dehydrated."

"Mary?" Kate asks, shaking her head as soon as she's downed the water. "What are you- what happened?"

"That guy over there shot you with an arrow and then Alice brought you to me." Mary says, nodding toward the man in question. "I patched you up."

It's then that Kate's face flashes with fear and Mary has to look away. "You don't have to worry, I'm not going to tell anyo-"

"Did Beth hurt you?" Kate interrupts Mary's attempt to assure her that she wouldn't betray Kate's secret.

"What?"

"Beth. Alice. She didn't try to hurt you did she?" Kate asks, real worry coloring her voice. Mary just stares at her, chest tightening with something painful but… not.

"Oh, no. I mean she kinda scared me half to death at first 'cause Red Alice and all that blood, _duh_, but- no, she didn't hurt me." Mary says and consciously stops herself from reaching up to rub at her neck, Alice hadn't really choked her, though she knows her skin well enough to know that by tomorrow there will be visible bruising there anyway.

"Good." Kate says, but her eyes are still running over Mary like she's cataloging every hair out of place, just to make sure it's true.

Mary doesn't quite know what to do with Kate's uncharacteristic reaction. So instead she changes the subject.

"Yeah," she says and her eyes slide sideways to the unspoken elephant of the room. "So, don't take this the wrong way but I really need Batwoman to not be here by the time it starts getting light outside."

She sees Kate flinch from the corner of her eye, as she too finally notices the Batwoman costume and maybe only now puts together all the pieces to realize exactly what Mary knows now.

For a moment Kate says nothing. Then she looks like she's weighing something and coming to a conclusion.

"It's okay. Luke can come pick me up, honestly I'm pretty sure he's already freaking out, I wasn't exactly supposed to go on a patrol yesterday. The suit's kinda of a mess right now. " Kate says with a shrug and then visibly regrets it as she winces and clutches at her stomach. "I just hadn't thought it was so much of a mess it would let a low speed projectile through."

"Yes, I'm guessing that's what happens when people jump on bombs, Kate." Mary quips back dryly.

"Yeah," she says, "about that."

"We can talk about that later." Mary says and then hands her another glass of water and two tablets of pain medication. "Drink that down. I'd give you some for later but you can afford to buy your own, and I'm already running low."

"What about him?" Kate asks as soon as she's followed Mary's instructions and nods toward her would-be killer. "He'll tell the cops where he'd tracked me to to cut a deal, or he'll tell his friends."

"Oh, no, it's fine, I've got guys in prison." Mary assures her.

"You've got guys in prison." Kate says, a wry twist to her mouth.

"It's not what it sound like, okay? It's just that, well, for some of them I'm the closest thing to health insurance their families have, so I'm like… officially off limits." Mary says and feels an embarrassed blush rising to her cheeks.

"Wow." Kate smirks.

"What!?" Mary can't help snapping, irritated and recalling all the times Kate made her feel smaller just by looking at her.

"My little stepsister really is the Meredith Grey of Gotham's underground." Kate teases her fondly, though her smile has slipped a bit and then drops completely at the sharp breath that catches in Mary's throat. "What?"

"Nothing, you've just never- it's nothing." Mary says, swallowing back the sudden and inexplicable tears threatening to build up and drop down her cheeks. She feels like Kate has just punched her in the chest, except somehow it's simultaneously the warmest feeling she remembers having.

—

The next time Mary sees Kate is a day later when she shows up at Mary's apartment carrying takeout from the Mexican place around the corner.

"I thought we should talk." Kate says when Mary opens the door.

"You should be in bed." Mary disagrees but lets her in, honestly she was kind of expecting her to come around, especially after she read today's front page article.

"I'm fine." Kate says.

Mary rolls her eyes and snorts.

"I sewed up your stomach yesterday, you needed a blood transfusion. You're really not." She guides her to the living room to sit down on the couch. For a few minutes there's a semi-comfortable silence as Mary sets up the dinner Kate brought over onto the table.

"I'm sorry I didn't tell you I was Batwoman." Kate says as soon as Mary has sat down beside her and started on her quesadilla.

"It's okay." Mary says but doesn't quite meet Kate's eyes, she's not lying but it still kind of stings. "I wish you would have trusted me but I get it."

"It wasn't about trust, Mary." Kate says. "I didn't want to put you in unnecessary danger."

"Well can you not put yourself in unnecessary danger either, please? I'd rather avoid as many future visits from Alice as possible." She says and unconsciously starts playing with the colorful silk scarf around her neck.

"So I take it you saw the article." Kate sighs.

Mary's eyes flicker toward the newspaper with a grimace.

"You mean the one about how Red Alice broke into police holding and killed a suspect found through an anonymous tip before he could be questioned? Yeah." She says, a stupid guilty feeling bubbling inside her chest cavity. "She said she wasn't going to kill him at my clinic, I should have guessed she meant that literally."

"It's not your fault, Mary."

"Right."

"It's not, you shouldn't-" Kate says and then freezes, eyes zeroing in on Mary's hand, the one running nervously over the scarf covering her neck. "What's that?"

"It's nothing, don't worry about it." Mary tries but isn't all that surprised to receive back a glare, so she sighs and removes the scarf hiding the bruises in the shape of a hand-print.

"I though you said Beth didn't hurt you." Kate whispers, voice upset.

"She didn't… much. I was gonna scream so she-"

"That's not an excuse, Mary."

"I know. It's just that all things considered this time went a lot better than last time, There were no axes for one." She tries joking to lighten the mood, it doesn't seem to work. "And she said she might actually be starting to like me now."

If anything, Kate looks even more worried at that.

"Yeah, that was pretty much my reaction too." Mary nods, it had felt like Alice had forgotten about her in the past two months and now she has a bad feeling that's no longer going to be the case.

Feeling like she needs to move on to a lighter subject she winds the silk back around her neck and grins a bit forcefully at Kate.

"So, you're Batwoman then, how did that happen?"

—

After that, their dinner is pretty uneventful. Kate fills her in on that whole vigilante business, though Mary's pretty sure she's still keeping something back. She doesn't fail to notice how in Kate's retelling of finding Batman's secret lair she never actually mentions any specifics.

But they do talk and it's not that different than it's been since Kate had come back to Gotham and they'd started actually hanging out sometimes, like how actual sisters might. They jump through topics, covering criminals Batwoman has taken down and patients Mary has patched up, the local barista Kate has been flirting with and the fellow med-student who's been hitting on Mary. She mentions the message Alice had wanted to convey to Kate and then they move back on to some lighter subjects when Kate's mood plummets.

Eventually it's getting late and Kate starts getting ready to go home… well, hopefully home. Or at least not out to patrol the city. Kate's definitely not healthy enough for that yet and Mary doesn't see how the Bat costume could have possibly gotten fixed this fast.

But before Kate can leave, Mary impulsively jumps forward to hug her. Squeezing her older stepsister for all it's worth - though she's careful not to put pressure near her abdomen. "I'm glad you didn't die."

"Mary?" Kate says but doesn't try to pull back, which means Mary doesn't feel like she has to either. It's not the first hug Mary's ever shared with Kate but it's the first one where Kate hasn't initially frozen, which puts this as the best hug she's ever gotten from Kate.

"Yeah?"

"I know I've never said this, and that I should have but I'm gonna say it now. I'm glad our parents married each other. I'm glad that we're family." Kate says and squeezes Mary back.

"Well, _duh_." Mary says and covertly tries to wipe away the tears before Kate can get the chance to see them. "I'm awesome."

*o0O0o*

**AN2**: I've always ALWAYS wanted to write an 'Identity Reveal' fic. But a properly interesting idea just never came to me and it just didn't happen. Until now.

And I really hope reading this brings you as much joy as writing it brought me.

Just FYI all of the medical stuff is stuff I could find by googling for half an hour and so it is definitely vastly inaccurate. Don't do this at home kids.

PLEASE tell me what you think.


End file.
